The explosive rise in popularity of smart phones has exposed the capacity limitation of current cellular communications networks. The increasing usage of bandwidth-demanding multimedia and social networking applications on mobile devices further exacerbates the problem. To cope with the exponential growth in wireless data traffic, it is anticipated that substantially denser deployment of access nodes will be required in the future. Such a dense deployment may be achieved by gradually augmenting existing base stations with a much denser mix of “smaller,” or low power, base stations with reduced signal footprints.
Clearly, the feasibility of a very dense deployment of access nodes is predicated on the existence of a backhaul network that can provide high-data-rate transport for each individual access node in the network. From the viewpoint of maximizing capacity, optical-fiber-based backhaul solutions are probably the most desirable ones and are most suitable for new constructions. However, in existing buildings and infrastructure, the cost of installation of new fibers to every access node in a very dense network can be prohibitive.
An alternative to an optical-fiber-based backhaul solution is a wireless self-backhaul solution where the same access spectrum is used to provide transport. A large amount of bandwidth is expected to be available in high frequency bands (e.g., the Millimeter Wave (MMW) bands) where future wireless systems are likely to be deployed. In addition, these future wireless systems have the potential of a high degree of spatial reuse due to the associated reduced radio wavelengths. Both the large amount of available bandwidth and the high degree of spatial reuse motivate the self-backhauling approach. The simplicity of the wireless self-backhaul approach and the potential of substantially reducing the deployment cost also make the wireless self-backhaul approach very attractive.
As illustrated in FIG. 1, in the self-backhauling approach, an access node (AN) provides network access to user equipments in its vicinity that are assigned to the access node as well as transport for neighboring access nodes. With regard to transport, the access node operates as a relay node in order to route data toward and/or from an aggregation node. A group of self-backhauling access nodes can form a wireless mesh network, where the access nodes cooperatively route each other's traffic to and from the aggregation node. The aggregation node connects the wireless mesh network to a larger network (e.g., a core network of the associated cellular communications network).
Not only does self-backhauling eliminate the need to install additional wires/fibers and hence substantially reduce deployment cost, self-backhauling also provides the ultimate flexibility for users or network operators to deploy access nodes anywhere there is unmet traffic demand. Even in the case when wired (fiber or copper based) backhaul is available, self-backhauling can still serve as a fallback or a diversifying solution to enhance the reliability of the network.
Transporting information wirelessly through a wireless mesh network formed by self-backhauling access nodes requires the use of routing algorithms in combination with a routing metric to select which route among all possible routes with one or more hops should be used. Common routing algorithms include the Bellman-Ford algorithm and the Dijkstra algorithm, as described in D. P. Bertsekas and R. G. Gallager, “Data Networks,” 2nd Edition, Prentice Hall, 1992. These algorithms typically find the shortest path (or route), in the sense of yielding the best routing metric value, among all possible paths from a source node to a destination node. The inventors have found that existing routing metrics, such as those described in Georgios Parissidis, “Interference-Aware Routing Wireless Multihop Network,” Doctoral Dissertation, DEA Universite Paris VI, 2008; R. Draves, J. Padhye, and B. Zill, “Routing in Multi-Radio Multi-Hop Wireless Mesh Networks,” ACM Mobicom, 2004; Y. Yang, J. Wang, R. Kravets, “Designing Routing Metrics for Mesh Networks,” Proc. IEEE Workshop on Wireless Mesh Networks, 2005; B. Awerbuch, D. Holmer, H. Ruberns, “High Throughput Route Selection in Multi-Rate Ad Hoc Wireless Networks,” Technical Report, Johns Hopkins University, 2003; A. Kamerman and L. Monteban, “WaveLAN-II: A High-Performance Wireless LAN for the Unlicensed Band,” Bell Labs Technical Journal, pp. 118-133, 1997; and G. Holland, N. Vaidya, and P. Bahl, “A Rate-Adaptive Protocol for Multi-hop Wireless Networks,” Proc. ACM MOBICOM 01, 2001 are less than optimal, particularly for wireless self-backhaul for a group of access nodes in a cellular communications network.